Cell Signalling lecture 1 ionic gradients and how they're established + voltage gated channels Flashcards
What are the three regulatory proteins?
metabolic enzyme (altered metabolism), gene regulatory protein (altered gene expression), cytoskeletal protein (altered cell shape or movement)
What can calcium signalling lead to ? (time domain)
gene transcription(min), metabolism(s), exocytosis (microseconds), contraction(ms), fertilisation(hr), proliferation(hr), hypertrophy (hr)
What is proliferation ?
Cell proliferation is the process that results in an increase of the number of cells, and is defined by the balance between cell divisions and cell loss through cell death or differentiation. Cell proliferation is increased in tumours.
What is hypertrophy ?
the enlargement of an organ or tissue from the increase in size of its cells.
Conc of Na+? mM
Intracellular 5-15
Extracellular 145
Conc of K+ ? Mm
Intracellular 140
Extracellular 5
Conc of Mg 2+ ? Mm
Intracellular 0.5
Extracellular 1-2
Conc Ca2+ ? Mm
Intracellular 10^-4
Extracellular 1-2
Conc of H+ ? Mm
Intracellular 7*10^-5 (10^-7.2M, pH 7.2)
Extracellular 4*10^-5 (10^-7.4M or pH7.4)
Conc of Cl-? Mm
Intracellular 5-15
Extracellular 110
What is the conc of Ca2+ in the ER?
0.5 mM
What is the approximate pH in lysosomes ?
4.5
What is the approximate pH in mitochondria ?
7.8
What does primary active transport require ?
ATP + H20 releasing energy and a phosphate ion
What type is the Na+/k+ pump ?
p-type ATPase
Describe the mechanism of the Na+/k+ pump ?
3Na+ bound ATP to ADP Phosphate group bound to pump 3Na+ out 2K+ bound phosphate group still bound phosphate group released 2 K+ in
How does calcium ionic gradient across the cell membrane established
?
PMCA which is a P-type ATPase pumps calcium out of the cell
How is the ionic gradient between the cytosol and the endoplasmic reticulum established ?
by SERCA which is a p-type ATPase that pumps calcium into the ER
What type of porter is the Na+/ca2+ exchanger ? how many transmembrane regions does the exchanger exhibit ?
Antiporter 3Na+ in down electrochemical gradient 2Ca2+ out against electrochemical gradient. 9
So how are ionic gradients established ?
by primary active transport and secondary transport (exchanger) ex na-k pump, pmca , serca which are all P-type ATPases, Na+/Ca2+ exchanger
How many transmembrane domains do K+ voltage gated ion channels exhibit ? how about Na+ or Ca2+?
- 4 (tetrameric) of which are voltage sensing domains. and 2 are pore domains. - 24
Why can’t Na+ pass down K+ ion channels ?
because the selectivity filter in the pore domain stabilises the larger dehydrated K+ ion by forming 4 electrostatic charges between O and K. Na+ only needs 2 electrostatic charges to be stabilised therefore it is rejected.
How is voltage sensed in voltage gated ion channels?
by positively charged residues in the S4 region. Regulary spaced arginine (R) and lysine (K) residues ‘sense’ potential changes which mediate a conformational change - s4 region pops up opening the ion channel
